Writing my own square root function

I have to write my own square root function using:
x=n-1
return 1+(1/2)x-(1/8)x^2+(1/16)x^3-(5/128)x^4

it will be named "doublemy_sqrt_1(double n)"

then write a main that prints n, sqrt(n) and my file for n=3.14159*10^kth for k=-100, -10, -1, 0, 1, 10, and 100.
I am supposed to use the code

for(auto k: {-100, -10, -1, 0, 1, 10, 100}){
                                     n=3.14159*pow(10.0, k);
                                       //cout goes here
                                       }

then I need to modify it so I can print the relative error as a percent, by adding a column

relative_error_per_cent=100*((my_sqrt_1(n)-sqrt(n))/sqrt(n)

. Line up the columns using

setw()

, ect.

THANKS IN ADVANCE!